1. Field of Art
The disclosure relates generally to reciprocating pumps, including mud pumps used in the recovery of oil and gas. More particularly, the disclosure relates to piston components for reducing wear to pump piston expendables and limiting leakage in the event of piston seal failure.
2. Description of Related Art
Mud pumps are commonly used for conveying drilling mud during well drilling operations, such as for the recovery of oil and gas. Because of the need to pump the drilling mud through several thousand feet of drill pipe, such pumps typically operate at high pressures. Also, it is necessary for the drilling mud to emerge from the drill bit at a high flow rate in order to provide lubrication and cooling to the bit and to provide a vehicle for removal of drill cuttings from the earth formation being drilled. Further, the pressure generated by the mud pump contributes to the total downhole pressure, which is used to prevent well blowouts.
Mud pump components, such as the piston, cylinder and sealing element, are susceptible to a high degree of wear during use because the drilling mud is highly pressurized and relatively dense with a high proportion of suspended abrasive solids. As the cylinder becomes worn, the small annular space between the cylinder wall and the piston increases substantially and sometimes irregularly. Moreover, the combined effect of the high-pressure, abrasive nature of the drilling mud and the frictional forces resulting from the reciprocating contact between the piston and the cylinder wall is especially harmful to the sealing element. As the piston moves, edges of the sealing element experience wear and may become damaged. In some instances, the frictional force may be sufficient to cause the sealing element to detach from the piston. Additionally, the sealing element is susceptible to impact and abrasion damage due to direct exposure to the drilling mud.
Because these components experience high wear rates, it is often necessary to replace them on a regular basis. When replacing these components, the mud pump must be deactivated, which interrupts the drilling operation and thus increases drilling time and cost. Accordingly, means for reducing wear to pump components to increase the service life of the mud pump and reduce drilling downtime are desirable. It would be advantageous if such means limit leakage in the event of sealing element failure so as to allow the pump to continue to operate for some time, rather than requiring immediate servicing or replacement.